|Theme||Visible||Selectable||Appearance||Zoom Range (now: 0)|
In this paper, we present for the first time, a classification system for naturally-occurring gas hydrate deposits existing in the permafrost and marine environment. This classification is relatively simple but highlights the salient features of a gas hydrate deposit which are important for their exploration and production such as location, porosity system, gas origin and migration path. We then show how this classification can be used to describe eight well-studied gas hydrate deposits in permafrost and marine environment. Potential implications of this classification are also discussed.
Tyagi, Anisha (California State Polytechnic University-Pomona) | Grenier, Margaret (California State Polytechnic University-Pomona) | Kreuziger, Rachel (California State Polytechnic University-Pomona) | Kays, Jacob (California State Polytechnic University-Pomona) | Polet, Jascha (California State Polytechnic University-Pomona)
The San Gabriel and San Bernardino Basins are sedimentary basins located in southern California that are surrounded by a network of faults and comprised of soft sediments. Sedimentary basins are known to amplify earthquake ground motions and increase their duration. The San Gabriel and San Bernardino Basins are densely populated areas; therefore, it is important to determine site characteristics for seismic hazard mitigation. Furthermore, if a major rupture were to occur on the Southern San Andreas Fault, the San Gabriel and San Bernardino Basins could potentially amplify the ground motion and funnel the energy from the rupture into the Los Angeles Basin (Denolle et al., 2014), acting as a waveguide. Therefore, it is important to better characterize these basins and to understand their resonance period, amplification and site response. Three seismic profiles, containing over 200 threecomponent nodes, were installed across the San Gabriel and San Bernardino Basins in the first quarter of 2017 and collected approximately one month of continuous waveform data. We apply the Horizontal-to-Vertical Spectral Ratio (HVSR) method to the ambient noise waveform data from this experiment. The resulting spectral ratio curves show clear long period peaks (between 2 and 5 seconds) that likely correspond to basin resonance and that indicate significant variation in amplification factors and resonance frequencies across both basins. Preliminary results show these long period peaks for nodes to the South of the Raymond Fault along a profile in the Western part of the San Gabriel Basin, as well as across the central part of this basin. The peak frequencies for the Western profile suggest that the basin is relatively deeper in this area. Nodes in the Southern half of the Chino Basin indicate values for peak frequencies between those measured for the San Gabriel Basin lines. Peak amplitudes vary between 2 and 4.5, which indicates potential for significant ground motion amplification.
Presentation Date: Wednesday, October 17, 2018
Start Time: 1:50:00 PM
Location: Poster Station 14
Presentation Type: Poster
Hogan, Phillip Joseph (Fugro West, Inc.) | Lane, Andrew (Woodside Energy Ltd. ) | Hooper, James (Fugro-McClelland Marine Geosciences) | Broughton, Aaron (Fugro West, Inc.) | Romans, Brian (Stanford University)
Geotechnical data, geochronologic data, and high resolution seismic data collected for Woodside's OceanWay Secure Energy LNG project allow an improved understanding of the tectonic and sedimentary processes in Santa Monica Bay and Basin, and identification of geologic hazards.
The proposed facilities are located in a deepwater basin near the collisional transform boundary of the Inner California Continental Borderland (ICB) Province with the Western Transverse Ranges (WTR) Provinces. This area is characterized by complex interactions between blind thrust faults underlying the Los Angeles Basin and strike slip faults related to the northwest motion of the Pacific Plate relative to North America. Active faults and folds crossing the proposed pipeline route present a ground rupture and deformation hazard on the continental slope.
Active sediment transport processes and high sediment accumulation rates are documented on Hueneme submarine fan in Santa Monica Basin (SMB). High-resolution seismic-reflection profiles across Ocean Drilling Program (ODP) borehole 1015 in the basin plain provide a well-dated chronostratigraphic record. Turbidity currents in Santa Monica Basin are sand-dominated, and have increased in sediment volume per event in the latest Holocene. Whilst some turbidites likely result from El Niño-Southern Oscillation (ENSO) storm events, others are believed to have been triggered by seismically-induced strong ground motions.
The potential exists for surface folding and fault rupture, seismically induced strong ground motions, and turbidity currents to affect the proposed pipeline within the lifetime of the project. These geohazards will be mitigated through appropriate analyses, risk studies, and engineering design of the OceanWay facilities, allowing safe and secure importation of natural gas to the West Coast of the USA.
Proposed LNG developments in deepwater offshore the West Coast of the United States face new challenges, both on technical issues such as facility engineering and from natural geologic processes. Many recent high-profile deepwater developments continue to encounter major geological hazards (geohazards) on an increasing scale worldwide.
Woodside Natural Gas, Inc. (Woodside) proposes to import LNG to Southern California via a Deepwater Terminal in SMB. SMB is one of several basins in the ICB, a tectonically active area along the plate boundary between the Pacific and North American Plates (Figure 1). A 56-km submarine pipeline will bring the gas ashore via a horizontal directional drill borehole at a landfall in the coastal portion of the Los Angeles Basin (Figure 2). Detailed feasibility and siting studies were performed in 2005 and 2006 to assist in the selection of the optimal location of the OceanWay Project. This paper summarizes geohazards identified during the 2006 geophysical and geotechnical surveys.
Rabinowitz, P.D. (Texas A&M University ) | Francis, T.J.G. (Texas A&M University ) | Baldauf, J.G. (Texas A&M University ) | Coyne, J.C. (Texas A&M University ) | McPherson, R.G. (Texas A&M University ) | Merrill, R.B. (Texas A&M University ) | Olivas, R.E. (Texas A&M University )
Ploessel, M.R. (McClelland Engineers, Inc.) | Crissman, S.C. (McClelland Engineers, Inc.) | Rudat, J.H. (McClelland Engineers, Inc.) | Son, R.R. (McClelland Engineers, Inc.) | Lee, C.F. (McClelland Engineers, Inc.) | Randall, R.G. (McClelland Engineers, Inc.) | Norton, M.P. (McClelland Engineers, Inc.)
An instrumented, tri-moor cable structure was implanted successfully using a phased implant technique in 2,900 feet of water in the Santa Monica Basin off Southern California. The experimental structure was constructed to provide a platform for evaluating cable structure design techniques and recent developments in ocean engineering technology.
The analytical model used to design the structure is described and predicted structure displacements due to two assumed current profiles are presented. Guidelines used in the mechanical and electrical design of the structure are outlined, and the subsystems and major components are described. The techniques which resulted in the successful implant are presented.
Although sufficient data are not yet available to evaluate in detail the analytical model used to design the structure, data obtained do indicate gross agreement between theory and actual performance.
All mechanical and most electrical equipment survived the implant. Although some component failures have occurred, the design philosophy has been successful in avoiding any subsystem failures.
During the past fifteen years numerous analytical models have been developed to analyze the steady-state behavior of moored cable systems. These models attempt to predict the tensions in the cables and the geometry of the moorings acted on by steady-state ocean currents. None of these models yield exact solutions because of the inexact assumptions regarding structural properties and hydrodynamic loading criteria and because of errors inherent in the computational techniques. 1 Because little experimental data exist to validate models, except those for designing very simple moors, precise validation data are needed to quantify the errors associated with the various techniques. 1 The SEACON II structure was designed and built primarily to satisfy this need for data on the steady-state response of a complex cable structure to ocean currents. An additional objective of the SEACON II project was to evaluate recent developments in ocean engineering technology while implanting and operating the cable structure.
The SEACON II structure (Figure 1) consists of a delta-shaped module tethered by three mooring legs (L1, L2, and L3) in 2,900 feet of water. Legs L1 and L2 are torque-balanced mechanical cables and L3 is a torque-balanced electromechanical (EM) cable. Each leg is 4,080 feet long. The delta module with 1,000-foot-long EM cable arms is positioned approximately 500 f be10w the surface and is buoyed at each apex by a 5½-foot-diameter spherical buoy (NBl, NB2, and NB3). The mechanical cable legs (Ll and L2) are anchored with experimental deep ocean explosive embedment anchors (AI and A2). The EM cable leg (L3) is anchored by a l2,500-pound clump anchor (A3) which contains a 10-watt radioisotope power generator (RPG). The anchors are positioned approximately 6600 feet apart. An EM wire rope crown line (CL) extends from the clump anchor to an 8-foot-diameter crown buoy (CB) 50 feet below the surface. Electronics and recording equipment is stored within a removable pressure canister in the crown buoy.